When observing a sample (wafer having an LSI pattern formed thereon) using an electron beam applied device, for example, scanning electron microscope (SEM: Scanning Electron Microscope), electron beams emitted from an electron gun are deflected by a scanning deflector so that a secondary electron, reflecting electron and backscatter electron generated from the sample surface are detected by electron beam scanning. The resultant signal is processed to capture an image.
FIG. 1 shows a generally employed scanning (hereinafter referred to as interlace scanning). A reference numeral 101 denotes a scanning order, 102 denotes a scanning line number, and 103 denotes a scanning area. In the generally employed image display process, a secondary electron signal obtained at a scanning position on the sample is transferred to an element (pixel) for image display so that the two-dimensional image is displayed. The elements for image display are arranged uniformly in horizontal/vertical directions. In case of the interlace scanning, after the horizontal scanning, one row in the vertical direction is skipped, and then the horizontal scanning is conducted again. The similar operation will be repeatedly conducted with respect to the skipped row. Japanese Patent Application Laid-Open Publication Nos. 2008-123716 and 5-151927 disclose the operation of the generally employed electron microscope.